Stationary bicycle trainers have been popular in the last few decades as a means to use an existing bicycle on a stationary device that provides resistance to pedaling without the need to also balance, as is required with a bicycle roller.
In the current art, most bicycle trainers and a variety of resistance mechanisms, that rely on the bicycle's own tire to drive a resistance device, use a framework to rigidly mount the rear wheel while holding the bicycle upright. In all of these applications, the resistance mechanism is located behind the rear wheel and pivotally attached to the framework below the resistance device, or “upstream” of the tire's direction of rotation. This is a convenient place to locate a pivot, and allows the driven cylinder of the resistance mechanism to be adjusted into the tire to a degree that reduces or eliminates slippage at the highest torque the cyclist can put out. This method of compressing a driven cylinder into the bicycle tire will be referred to as “Fixed Compression” herein.
For example; for a cyclist to put out a maximum of 700 watts the resistance device must compress the rear tire sufficiently to prevent slipping. Realistically, however, most of the time a user will spend on a trainer is at much lower wattage, such as 150 to 200. Therefore, most of the time the tire is compressed and distressed unnecessarily.
This causes three problems; A) the tire will wear quickly if it is highly distressed. In fact, many manufacturers make a special “trainer tire” that is a harder rubber compound capable of lasting longer in trainers. These tires cannot be used on the road because their hard composition causes reduced coefficient of friction to a road surface and is relatively easy for a cyclist to lose control. B) high distress at low power consumes power that limits the minimum effort for the cyclist and C) high distress with no power input consumes inertia from relatively light bicycle wheels, requiring heavier flywheels to compensate for the loss. Bicycle trainer manufacturers typically design for a certain degree of inertia to provide for a smooth stroke since it is nearly impossible to power through a 360 degree pedal rotation with constant power. Uneven power application will cause exaggerated changes in wheel speed, especially with lightweight bicycle wheels unless a heavier flywheel (integral to the bicycle trainer) is employed to better control wheel speed, acceleration, and deceleration. An improved tire compression device is needed.